Comparison of diverse platelet activation markers as indicators for left atrial thrombus in atrial fibrillation

Asymmetric dimethylarginine correlates with indicators of prethrombotic state in patients with nonvalvular atrial fibrillation

OBJECTIVE

The mechanism of asymmetric dimethylarginine (ADMA) in thrombosis in patients with nonvalvular atrial fibrillation (NVAF) is still unclear. Our aim was to investigate the relationship between ADMA and indicators of prethrombotic state in NVAF patients and to analyze the predictive role of ADMA in NVAF thrombosis.

METHODS

A total of 192 NVAF patients were continuously selected from January 2023 to October 2023. Plasma ADMA levels were measured by high-performance liquid chromatography. P-selectin (P-sel), von Willebrand factor (vWF), D-dimer (D-D), and plasminogen activator inhibitor-1 (PAI-1) levels were measured by enzyme-linked immunosorbent assay (ELISA). Nitric oxide (NO) levels were measured by the nitrate reductase assay for plasma nitrite/nitrate, then the Griess method (Shanghai Hailian Biotechnology Co., Shanghai, China) was used to calculate plasma NO levels.

RESULTS

In our study, ADMA levels were significantly elevated and positively correlated with P-sel, vWF, D-D, and PAI-1, whereas NO levels were significantly negatively correlated with these prethrombotic factors in NVAF. Furthermore, multifactorial logistic regression analysis showed that ADMA and LA diameter were independent predictors of high thrombosis risk (CHA2DS2-VASc ≥2 score) in patients with NVAF.

CONCLUSIONS

Our findings suggested that ADMA correlated with the prethrombotic state in NVAF and that reduction of ADMA levels in NVAF patients may be a novel therapeutic strategy for thrombosis risk reduction.

Atrial fibrillation and stroke

INTRODUCTION

Stroke is one of the leading causes of mortality and morbidity globally. Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. It is set to reach epidemic proportions. AF is associated with a five-fold increase in risk of stroke. Strokes caused by AF more often are fatal or result in severe disability. Even though the incidence of stroke has been significantly reduced by oral anticoagulation, AF is thought to account for a significant proportion of cryptogenic strokes where no etiology is identified.

AREAS COVERED

This article reviews the literature related to AF and stroke, pathophysiological insights, diagnosis of AF in stroke patients, and its management (Graphical Abstract).

EXPERT OPINION

The pathophysiology of thrombogenesis that links AF and stroke is not well understood and is an area of active research to identify new therapeutic targets to prevent AF and stroke. As the nature of AF and stroke is multifaceted, an integrated care approach to managing AF and stroke is increasingly essential.

Role of New Potential Biomarkers in the Risk of Thromboembolism in Atrial Fibrillation

Ischemic stroke risk in atrial fibrillation differs from patient to patient, depending on numerous variables. Many attempts have been made to translate this difference into simple numbers and to compare it to the hemorrhagic risk of anticoagulation. Different clinical scores have been studied to define a clear strategy. One score, the CHA₂DS₂-VASc score, has been extensively and successfully applied worldwide. Nevertheless, it is not yet the “perfect instrument”. Many proposals have been made to integrate its clinical parameters with some biomarkers to improve its predictive power. This short review describes some of these biomarkers and their possible implications in potentiating the efficacy of clinical scores.

Comparison of Immature Platelet Fraction and Factors Associated with Inflammation, Thrombosis and Platelet Reactivity Between Left and Right Atria in Patients with Atrial Fibrillation

Background

Recent trials found poor temporal relationship between atrial fibrillation (AF) episodes and strokes. Thus, stroke in AF patients probably involves more mechanisms than cardiac embolism. We compared factors of inflammation, thrombosis and platelet reactivity between left (LA) and right atria (RA) and femoral vein (FV) in patients with AF.

Methods

Blood samples were collected from patients undergoing AF-ablation from the FV, RA and LA for neutrophil to lymphocyte ratio (NLR), immature platelet fraction (IPF) and count (IPC), CD40 ligand, P-selectin and E-Selectin. IPF was measured by an autoanalyzer; CD40 ligand, P-selectin, and E-Selectin were measured by ELISA and NLR was calculated from complete blood counts.

Results

Sixty-seven patients were included (age 65±10y, 63% male, CHA₂DS₂-VASc score 2.8±1.8, LA volume index 40±24 mL/m², 63% paroxysmal AF). There was no difference between FV, RA and LA regarding NLR and CD40 ligand. Factors associated with platelets activity: P-selectin, IPC and IPF% were higher in RA vs LA (60.3 IQR 49.0-76.4 ng/ml vs. 59.3 IQR 49.0-74.7, respectively, p=0.03 for P-selectin, 7.5 IQR 5.2-10 103/μL vs. 7.1 IQR 5-9.8, p<0.01 for IPC, and 3.6 IQR 2.7-5.0 % vs. 3.6 IQR 2.6-4.8, p<0.01 for IPF%). Similar trends were for E-selectin (41.2 IQR 31.1-51.2 ng/mL vs. 38.7 IQR 27.9-50.4 p=0.09). Similar significant differences were found in patients with CHA₂DS₂-VASC≥2 but not in patients with low score.

Conclusions

Patients with AF, especially those with CHA₂DS₂-VASc≥2, have higher markers of thrombogenicity in RA compared to LA. There was no difference in inflammatory properties between the atria.

Diagnostic accuracy of D-dimer to detect left atrial thrombus in patients with atrial fibrillation: A systematic review and meta-analysis

BACKGROUND

There is conflicting evidence about the use of biomarkers to diagnose left atrial thrombus in patients with atrial fibrillation.

OBJECTIVE

The purpose of this study was to assess the diagnostic accuracy of D-dimer to detect left atrial thrombus in patients with atrial fibrillation.

METHODS

We searched 4 electronic databases from inception to December 16, 2020. The reference standard was left atrial thrombus detected by transesophageal echocardiography. Study quality was assessed with the Quality Assessment of Diagnostic Accuracy Studies 2 tool. We used a bivariate model to calculate the pooled sensitivity and specificity with their 95% confidence intervals (CIs). The optimal cutoff and predictive values were also estimated.

RESULTS

Eleven cross-sectional studies involving 4380 patients were included. The median prevalence of left atrial thrombus was 12%. In 7 studies, the pooled sensitivity of D-dimer at 500 ng/mL was 50% (95% CI 26%-74%) and the pooled specificity was 88% (95% CI 76%-95%). The pooled sensitivity of age-adjusted D-dimer was 36% (95% CI 14%-66%) and the pooled specificity was 99% (95% CI 96%-99%) in 2 studies. The optimal cutoff of D-dimer was 390 ng/mL in 10 studies with a pooled sensitivity of 68% (95% CI 44%-85%) and a pooled specificity of 73% (95% CI 54%-86%). The positive and negative predictive values were 21.8% and 95.4%, respectively. The risk of bias was low or unclear for all domains. Concerns about applicability were low for almost all studies.

CONCLUSION

Our meta-analysis suggests that D-dimer has the potential to be useful to rule out left atrial thrombus in patients with atrial fibrillation.

[Independent risk factors of atrial thrombosis in patients with nonvalvular atrial fibrillation and low CHA2DS2-VASc scores]

OBJECTIVE

To explore the risk factors of atrial thrombosis in patients with nonvalvular atrial fibrillation(NVAF)with low CHA₂DS₂-VASc scores at admission (≤1 for male and ≤2 for female patients).

METHODS

We retrospectively analyzed the clinical data of 10 382 patients with NVAF undergoing transesophageal echocardiography in our hospital from 2009 to 2019, and enrolled 48 NVAF patients with thrombosis as the observation group and another 240 NVAF patients without thrombosis as the control group.The baseline characteristics, biochemical indicators, and echocardiographic findings of the patients were analyzed using univariate analysis, multivariate logistic regression analysis and Pearson correlation analysis.

RESULTS

The baseline data did not differ significantly between the two groups (P > 0.05).Compared with those in the control group, the patients with atrial thrombosis had an increased left atrial diameter (LAD; P < 0.001), a greater likelihood of hypertrophic cardiomyopathy (HCM; P < 0.001), significantly higher levels of C-reactive protein (CRP; P < 0.05) and uric acid (P < 0.001), and greater standard deviation of red blood cell distribution width(RDW-SD; P < 0.001).LAD(P < 0.001), HCM(P < 0.05)and CRP(P < 0.05) were identified as the independent factors affecting the occurrence of atrial thrombosis in patients with low CHA₂DS₂-VASc scores.

CONCLUSIONS

LAD enlargement, HCM, and an elevated CRP level are independent risk factors for atrial thrombosis in NVAF patients with low CHA₂DS₂-VASc scores.Active anticoagulation therapy should be administered for these patients once these risk factors are detected to prevent the occurrence of stroke.

Exosomes in atrial fibrillation: therapeutic potential and role as clinical biomarkers

Atrial fibrillation (AF), the most common cardiac arrhythmia, is a global epidemic. AF can cause heart failure and myocardial infarction and increase the risk of stroke, disability, and thromboembolic events. AF is becoming increasingly ubiquitous and is associated with increased morbidity and mortality at higher ages, resulting in an increasing threat to human health as well as substantial medical and social costs. Currently, treatment strategies for AF focus on controlling heart rate and rhythm with medications to restore and maintain sinus rhythm, but this approach has limitations. Catheter ablation is not entirely satisfactory and does not address the issues underlying AF. Research exploring the mechanisms causing AF is urgently needed for improved prevention, diagnosis, and treatment of AF. Exosomes are small vesicles (30-150 nm) released by cells that transmit information between cells. MicroRNAs in exosomes play an important role in the pathogenesis of AF and are established as a biomarker for AF. In this review, a summary of the role of exosomes in AF is presented. The role of exosomes and microRNAs in AF occurrence, their therapeutic potential, and their potential role as clinical biomarkers is considered. A better understanding of exosomes has the potential to improve the prognosis of AF patients worldwide, reducing the global medical burden of this disease.

A Review of Biomarkers for Ischemic Stroke Evaluation in Patients With Non-valvular Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia worldwide and results in a significantly increased ischemic stroke (IS) risk. IS risk stratification tools are widely being applied to guide anticoagulation treatment decisions and duration in patients with non-valvular AF (NVAF). The CHA₂DS₂-VASc score is largely validated and currently recommended by renowned guidelines. However, this score is heavily dependent on age, sex, and comorbidities, and exhibits only moderate predictive power. Finding effective and validated clinical biomarkers to assist in personalized IS risk evaluation has become one of the promising directions in the prevention and treatment of NVAF. A number of studies in recent years have explored differentially expressed biomarkers in NVAF patients with and without IS, and the potential role of various biomarkers for prediction or early diagnosis of IS in patients with NVAF. In this review, we describe the clinical application and utility of AF characteristics, cardiac imaging and electrocardiogram markers, arterial stiffness and atherosclerosis-related markers, circulating biomarkers, and novel genetic markers in IS diagnosis and management of patients with NVAF. We conclude that at present, there is no consensus understanding of a desirable biomarker for IS risk stratification in NVAF, and enrolling these biomarkers into extant models also remains challenging. Further prospective cohorts and trials are needed to integrate various clinical risk factors and biomarkers to optimize IS prediction in patients with NVAF. However, we believe that the growing insight into molecular mechanisms and in-depth understanding of existing and emerging biomarkers may further improve the IS risk identification and guide anticoagulation therapy in patients with NVAF.

Soluble Platelet Release Factors as Biomarkers for Cardiovascular Disease

Platelets are the main players in thrombotic diseases, where activated platelets not only mediate thrombus formation but also are involved in multiple interactions with vascular cells, inflammatory components, and the coagulation system. Although in vitro reactivity of platelets provides information on the function of circulating platelets, it is not a full reflection of the in vivo activation state, which may be relevant for thrombotic risk assessment in various disease conditions. Therefore, studying release markers of activated platelets in plasma is of interest. While this type of study has been done for decades, there are several new discoveries that highlight the need for a critical assessment of the available tests and indications for platelet release products. First, new insights have shown that platelets are not only prominent players in arterial vascular disease, but also in venous thromboembolism and atrial fibrillation. Second, knowledge of the platelet proteome has dramatically expanded over the past years, which contributed to an increasing array of tests for proteins released and shed from platelets upon activation. Identification of changes in the level of plasma biomarkers associated with upcoming thromboembolic events allows timely and individualized adjustment of the treatment strategy to prevent disease aggravation. Therefore, biomarkers of platelet activation may become a valuable instrument for acute event prognosis. In this narrative review based on a systematic search of the literature, we summarize the process of platelet activation and release products, discuss the clinical context in which platelet release products have been measured as well as the potential clinical relevance.

Increased Levels of Platelets and Endothelial-Derived Microparticles in Patients With Non-Valvular Atrial Fibrillation During Rivaroxaban Therapy

It is known that atrial fibrillation (AF) is associated with the procoagulant state. Several studies have reported an increase of circulating microparticles in AF, which may be linked to a hypercoagulable state, atrial thrombosis and thromboembolism. We evaluated in our study alterations in both platelet (PMP, CD42b) and endothelial-derived (EMP, CD144) microparticle levels on anticoagulant therapy with rivaroxaban in nonvalvular AF. After administration of rivaroxaban, PMP levels were increased (median, [IQR] 35.7 [28.8-47.3] vs. 48.4 [30.9-82.8] cells/µL; P = 0.012), along with an increase in EMP levels (14.6 [10.0-18.6] vs. 18.3 [12.9-37.1] cells/µL, P < 0.001). In the multivariable regression analysis, the independent predictor of post-dose change in PMPs was statin therapy (HR −0.43; 95% CI −0.75,−0.10, P = 0.011). The post-dose change in EMPs was also predicted by statin therapy (HR −0.34; 95% CI −0.69, −0.01, P = 0.046). This study showed an increase in both EMPs and PMPs at the peak plasma concentration of rivaroxaban. Statins have promising potential in the prevention of rivaroxaban-related PMP and EMP release. The pro-thrombotic role of PMPs and EMPs during rivaroxaban therapy requires further study.

Update on Biomarkers Associated to Cardioembolic Stroke: A Narrative Review

Background: In the last years, several studies were conducted that evaluated biomarkers that could be helpful for cardioembolic stroke diagnosis, prognosis, and the determination of risk of stroke recurrence. Methods: We performed a narrative review of the main studies that evaluated biomarkers related to specific cardioembolic causes: atrial fibrillation, patent foramen ovale, atrial cardiomyopathy, and left ventricular wall motion abnormalities. Results: BNP and NT-proBNP are, among all biomarkers of cardioembolic stroke, the ones that have the highest amount of evidence for their use. NT-proBNP is currently used for the selection of patients that will be included in clinical trials that aim to evaluate the use of anticoagulation in patients suspected of having a cardioembolic stroke and for the selection of patients to undergo cardiac monitoring. NT-proBNP has also been incorporated in tools used to predict the risk of stroke recurrence (ABC-stroke score). Conclusions: NT-proBNP and BNP continue to be the biomarkers most widely studied in the context of cardioembolic stroke. The possibility of using other biomarkers in clinical practice is still distant, mainly because of the low methodological quality of the studies in which they were evaluated. Both internal and external validation studies are rarely performed for most biomarkers.

Differences in D-dimer blood concentration in atrial fibrillation patients with left atrial thrombus or severe left atrial spontaneous echo contrast

PURPOSE

Severe left atrial spontaneous echo contrast (SLASEC) is considered the prior stage to thrombosis and a high-risk factor for thrombotic events. Studies have suggested an effect of D-dimer blood concentration on exclusion of left atrial thrombus (LAT), but it remains unclear whether D-dimer concentrations differ between atrial fibrillation (AF) patients with SLASEC or LAT.

METHODS

Nonvalvular AF patients scheduled to undergo catheter ablation or cardioversion in Shanghai Ruijin Hospital between January 2017 and July 2020 were screened for this prospective study. All patients underwent transesophageal echocardiography (TEE) to detect SLASEC or LAT. D-dimer concentrations were measured at the time of TEE. Clinical data including CHA₂DS₂-VASc score were evaluated. Major complications with thromboembolism in the SLASEC group were followed up at least 6 months after therapy.

RESULTS

Among 920 consecutively enrolled nonvalvular AF patients, 30 patients with SEC grade 0, 35 patients with SLASEC, and 22 patients with LAT were included. D-dimer concentration and CHA₂DS₂-VASc score were significantly lower in the SLASEC group compared with the LAT group (D-dimer, 0.26±0.13 vs. 0.86±0.9 mg/L, P<0.05; CHA₂DS₂-VASc score, 2.3±0.9 vs. 3.1±1.5, P=0.02). The cut-off value for D-dimer concentration (0.285 mg/L) had sensitivity of 77.3% and specificity of 80.0% for prediction of LAT. D-dimer concentration showed a decreasing trend with a significant difference (0.42±0.22 vs. 0.33±0.18 mg/L, P=0.03) for 9 patients in the LAT group after complete thrombus resolution by anticoagulation treatment. No major or fatal bleeding, ischemic stroke, or systemic thromboembolism events occurred in the SLASEC group during the 6-month follow-up.

CONCLUSIONS

This study demonstrated a significantly lower D-dimer concentration and CHA₂DS₂-VASc score in AF patients with SLASEC than in those with LAT. The D-dimer cut-off value (0.285 mg/L) can be used as an effective reference index to distinguish the pre-thrombotic state of LAT from LAT. D-dimer blood concentration may be a predictor of LAT thrombolysis.

Extracellular vesicles in atrial fibrillation and stroke

BACKGROUND

Atrial fibrillation (AF) is associated with a 5-fold increased risk of thromboembolic stroke. Extracellular vesicles (EVs) convey pathophysiological information and are possible biomarkers for risk of stroke.

METHODS

EVs were measured in 836 patients with AF (of which 280 were stroke cases) selected from the ARISTOTLE trial and in a cohort of unselected 70 year old individuals (n = 1007, reference material). EVs from platelets, leukocytes, erythrocytes and inflammatory endothelial cells were measured using flow cytometry and a solid-phase proximity ligation assay.

RESULTS

Concentrations of EVs were higher in the ARISTOTLE patients than in the PIVUS cohort for all the EV groups except EVs from endothelial cells (p < 0.0001). The distributions of the concentrations of the EVs were similar among the control group and the stroke cases for all of the sources of EVs in the ARISTOTLE study. EVs were modestly correlated with the levels of NT-ProBNP, Cystatin C, GDF-15 and D-dimer. Stronger correlations were found for platelet EVs as well as phosphatidyl serine positive EVs that were correlated with CD40 ligand in the ARISTOTLE study. Leukocyte EVs were correlated with IL-6 in both the ARISTOTLE and the PIVUS study, implicating them in different physiological processes.

CONCLUSIONS

Higher levels of EVs were found in anticoagulated patients with AF and a higher risk of stroke than in a general population of similar age, possibly due to the high disease burden in AF patients. Our data with EVs representing a broad repertoire of activated blood cells in AF patients suggest that EVs are likely not a key mediator of occurrence of stroke in this population.

CD11b expression on monocytes and data of inflammatory parameters after Transcatheter Aortic Valve Implantation in dependence of early mortality

An inflammatory systemic reaction is common after Transcatheter Aortic Valve Implantation (TAVI). We recently reported about an involvement of Mon2-monocytes, the CD11b expression on monocytes and parameters of systemic inflammation before TAVI correlating with early mortality after TAVI. Here, we provide data of monocyte subpopulations, CD11b expression and parameters of a systemic inflammation in dependence of three-month mortality after TAVI. With this, we provide further insights into inflammatory mechanism after TAVI. The data were collected by flow-cytometric quantification analyses of peripheral blood in 120 consecutive patients who underwent TAVI (on day 1 and 7 after TAVI). Monocyte-subsets were identified by their CD14 and CD16 expression and monocyte-platelet-aggregates (MPA) by CD14/CD41 co-expression. The extent of monocyte activation was determined by quantification of CD11b-expression (activate epitope). Additionally, pro-inflammatory cytokines such as interleukin (IL)-6, IL-8, C-reactive protein, procalcitonin were measured using the cytometric bead array method or standard laboratory tests. Additionally, we report procedural outcomes in dependence of three-month mortality. Furthermore, correlations of CD11b-expression on monocytes with parameters of platelet activation or further inflammatory parameters are presented. For further interpretation of the presented data, please see the research article “Mon2-Monocytes and Increased CD-11b Expression Before Transcatheter Aortic Valve Implantation are Associated with Earlier Death” by Pfluecke et al.[1]

Evidence-Based Case Report: The Use of D-Dimer Assay to Exclude Left Atrial Thrombus in Patient with Atrial Fibrillation >48 Hours

Introduction

Patients with atrial fibrillation (AF) for >48 hours who are a candidate for cardioversion should have transesophageal echocardiography (TEE) performed to exclude left atrial thrombus (LAT) that may cause systemic thromboembolism upon conversion to sinus rhythm. However, TEE facilities were limited, especially in developing countries.

Case Illustration

A 50 years-old man presented with exertional dyspnea and palpitation for 72 hours prior to admission. Electrocardiography showed AF with a ventricular rate of 140x/minute. Cardioversion was decided to be the best approach. This patient has an AF >48 hours of onset, hence, LAT should be excluded by the use of TEE. Unfortunately, there was no TEE facility nearby.

Discussion

Upon comprehensive search on the use of D-Dimer assay to exclude the LAT in AF patients, we found seven studies showed increased D-dimer level in those with left atrial thrombus. In 4 studies, AUC was > 0.70, sensitivity and specificity varied from 75.9% to 89% and 73.1% to 95% respectively. However, there is no single cut-off point, due to the heterogeneity of cut-off points.

Conclusion

D-dimer assay combined with other variables of atrial thrombus exclusion score is valuable in excluding LAT. Previously, weeks of anticoagulation is more advisable before attempting cardioversion in the absence of nearby TEE facilities. With current evidence, a low D-dimer and ATE score of 0 is safe for cardioversion.